The majority of yarns produced at present are spun with real twist. In one method of manufacture, spun yarns are produced by firstly straightening and untangling fibres by a carding-type process, to produce a flat web of fibres which is then divided across its width into narrow ribbons which are passed between rubbing aprons to consolidate the fibres into rounded and continuous structures, called slubbings. Such slubbings and like loosely joined lengths of fibres for use in spinning processes may be completely untwisted or they may have a slight degree of twist or false twist sufficient to enable them to be handled easily prior to spinning. Conventionally, slubbings may be provided with up to about one-half turn of twist per inch of length and as such they tend to have a low tensile strength and can easily be pulled apart by hand. The slubbings are then formed into yarns for weaving, knitting and other purposes by spinning processes and machinery, which can be quite complicated for commercial operations. The strength of the finished yarn is in most instances determined by the extent or degree of twisting of the fibres into their interlocked form i.e. the tighter the twist, the stronger the finished yarn. However, the tighter twisting also reduces the thickness of the finished yarn and creates a ‘hardness’ to fabrics woven from or articles knitted with such tight spun yarns. In the case of natural wool like fibre yarns and fabrics or articles produced therefrom, there is a loss of the desirable springy soft feel and thermal insulation qualities inherent with unspun or partially spun fibre yarns and fabrics/articles produced therewith.
A further problem with typical spun yarns (being a problem that increases with tighter spinning), is that when released from the tension applicable when the yarn is wound into a tight ball or onto a bobbin i.e. on unwinding for use in fabric or article forming, there is the tendency of the yarn to at least partially untwist. This can lead to entanglement and/or difficulties in feed to needles and/or machinery for processing; and in some instances can create a tendency in a finished fabric or article to twist out of the desired finished shape. Similarly, fibrous ropes, strings, cords and the like formed with tightly spun fibres in a similar manner to spun yarns can be prone to a partial untwisting tendency and entanglement when released from a coil.
Hereinafter, for ease of reference, articles conventionally produced by the spinning processes described above will be referred to by the term “spun yarns”.
U.S. Pat. No. 4,003,194 discloses a yarn with a core of false-twisted or loosely twisted or untwisted fibres and a wrapping of threads or fibres helically wound in one direction around the outside of the core. In this arrangement, as there is relative twist between the core and the wrapping, the wrapping tends to untwist if the yarn is cut or snagged.
U.S. Pat. No. 3,458,987 discloses a variation of this type of yarn structure in which the wrapping is formed from threads helically wound in opposite directions around the core, and the wrapping threads are melted or glued so that they adhere to each other at their cross-over points. Due to the complexity of this arrangement, the manufacturing process is very expensive and the yarn is produced at a relatively low rate.
In New Zealand Patent No. 194391, the present inventor addressed the problems associated with the prior art by providing an unspun yarn with an interlocked stitched cover to provide constraint and support for the fibre assembly or core. It will be apparent to the person skilled in the art that the production of such yarn is largely dependent upon the speed of operation of the stitch-forming machine. Here again, the production rate can be relatively low.
An object of the present invention is to provide an unspun fibre yarn having equal or greater strength than many conventional spun fibre yarns (produced from similar fibres), and without the inherent tendency to twist or untwist common to such conventional spun yarns.
Another object of the invention is to provide a method and means for producing a relatively high strength yarn utilising predominantly loosely joined drawn or carded fibres (slubbings) in conjunction with longitudinal reinforcing threads and without spinning in the conventional manner on conventional yarn spinning machinery, so that the end product yarn retains the fibres in a relatively loose format secured against accidental lateral and longitudinal separation.
Further objects of the invention are to provide a versatile unspun fibre high strength yarn capable of high speed and relatively low cost production in comparison with conventionally spun yarns, and to provide the method and machinery by which the unspun fibre yarn can be produced.
Other and more particular objects and advantages of the invention will become apparent from the ensuing description.